diff --git a/crypto/bn/bn_lcl.h b/crypto/bn/bn_lcl.h
index bab2c9d7056902083064320afbe9883107671ca8..f57c87d9b3670373512f3701fe4e7d4cc14b603e 100644
--- a/crypto/bn/bn_lcl.h
+++ b/crypto/bn/bn_lcl.h
@@ -23,10 +23,6 @@
 
 # include "internal/bn_int.h"
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 /*
  * These preprocessor symbols control various aspects of the bignum headers
  * and library code. They're not defined by any "normal" configuration, as
@@ -659,8 +655,4 @@ static ossl_inline BIGNUM *bn_expand(BIGNUM *a, int bits)
     return bn_expand2((a),(bits+BN_BITS2-1)/BN_BITS2);
 }
 
-#ifdef  __cplusplus
-}
-#endif
-
 #endif
diff --git a/crypto/cms/cms_lcl.h b/crypto/cms/cms_lcl.h
index c277f713767bea8b0def190ea22b539ded61074d..dd5a58529f6c8408437ef97a8659cae59589b9b6 100644
--- a/crypto/cms/cms_lcl.h
+++ b/crypto/cms/cms_lcl.h
@@ -10,10 +10,6 @@
 #ifndef HEADER_CMS_LCL_H
 # define HEADER_CMS_LCL_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 # include <openssl/x509.h>
 
 /*
@@ -438,7 +434,4 @@ DECLARE_ASN1_ITEM(CMS_RevocationInfoChoice)
 DECLARE_ASN1_ITEM(CMS_SignedData)
 DECLARE_ASN1_ITEM(CMS_CompressedData)
 
-#ifdef  __cplusplus
-}
-#endif
 #endif
diff --git a/crypto/engine/eng_int.h b/crypto/engine/eng_int.h
index 60fdf820f05513bd83e36b83030db5ed5b986859..7c41da2fe175e569253deabb0ef634fdd7a7891e 100644
--- a/crypto/engine/eng_int.h
+++ b/crypto/engine/eng_int.h
@@ -16,10 +16,6 @@
 # include "internal/thread_once.h"
 # include "internal/refcount.h"
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 extern CRYPTO_RWLOCK *global_engine_lock;
 
 /*
@@ -172,8 +168,4 @@ typedef struct st_engine_pile ENGINE_PILE;
 
 DEFINE_LHASH_OF(ENGINE_PILE);
 
-#ifdef  __cplusplus
-}
-#endif
-
 #endif                          /* HEADER_ENGINE_INT_H */
diff --git a/crypto/hmac/hmac_lcl.h b/crypto/hmac/hmac_lcl.h
index 4c156dc126c229c5b946e9faca52ca3675420f62..7ba0aac483ead8e06b0aa24002f61e088a1a18af 100644
--- a/crypto/hmac/hmac_lcl.h
+++ b/crypto/hmac/hmac_lcl.h
@@ -10,13 +10,6 @@
 #ifndef HEADER_HMAC_LCL_H
 # define HEADER_HMAC_LCL_H
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-#if 0                            /* emacs indentation fix */
-}
-#endif
-
 struct hmac_ctx_st {
     const EVP_MD *md;
     EVP_MD_CTX *md_ctx;
@@ -26,8 +19,4 @@ struct hmac_ctx_st {
     unsigned char key[HMAC_MAX_MD_CBLOCK];
 };
 
-#ifdef __cplusplus
-} /* extern "C" */
-#endif
-
 #endif
diff --git a/crypto/include/internal/aria.h b/crypto/include/internal/aria.h
index 073827185a398dbaa8907897def7a81d6b1bc8d0..e402b8eec803c3811f2b697103c31d4c366fad50 100644
--- a/crypto/include/internal/aria.h
+++ b/crypto/include/internal/aria.h
@@ -25,10 +25,6 @@
 # define ARIA_BLOCK_SIZE    16  /* Size of each encryption/decryption block */
 # define ARIA_MAX_KEYS      17  /* Number of keys needed in the worst case  */
 
-# ifdef  __cplusplus
-extern "C" {
-# endif
-
 typedef union {
     unsigned char c[ARIA_BLOCK_SIZE];
     unsigned int u[ARIA_BLOCK_SIZE / sizeof(unsigned int)];
@@ -51,8 +47,4 @@ int aria_set_decrypt_key(const unsigned char *userKey, const int bits,
 void aria_encrypt(const unsigned char *in, unsigned char *out,
                   const ARIA_KEY *key);
 
-# ifdef  __cplusplus
-}
-# endif
-
 #endif
diff --git a/crypto/include/internal/bn_int.h b/crypto/include/internal/bn_int.h
index ac49d1eab3d22a668094bc5588e507b2e4ce7d89..9379951dead6b50d9a005f899bcfaae627297711 100644
--- a/crypto/include/internal/bn_int.h
+++ b/crypto/include/internal/bn_int.h
@@ -13,10 +13,6 @@
 # include <openssl/bn.h>
 # include <limits.h>
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 BIGNUM *bn_wexpand(BIGNUM *a, int words);
 BIGNUM *bn_expand2(BIGNUM *a, int words);
 
@@ -64,8 +60,4 @@ void bn_set_static_words(BIGNUM *a, BN_ULONG *words, int size);
  */
 int bn_set_words(BIGNUM *a, BN_ULONG *words, int num_words);
 
-#ifdef  __cplusplus
-}
-#endif
-
 #endif
diff --git a/crypto/include/internal/chacha.h b/crypto/include/internal/chacha.h
index 7d4366ea25338198d5e71d68b9be75ce34a427b2..119361d4d86293f1515ed3ccf37e3240006f2120 100644
--- a/crypto/include/internal/chacha.h
+++ b/crypto/include/internal/chacha.h
@@ -12,10 +12,6 @@
 
 #include <stddef.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /*
  * ChaCha20_ctr32 encrypts |len| bytes from |inp| with the given key and
  * nonce and writes the result to |out|, which may be equal to |inp|.
@@ -43,7 +39,4 @@ void ChaCha20_ctr32(unsigned char *out, const unsigned char *inp,
 #define CHACHA_CTR_SIZE		16
 #define CHACHA_BLK_SIZE		64
 
-#ifdef __cplusplus
-}
-#endif
 #endif
diff --git a/crypto/include/internal/sm2.h b/crypto/include/internal/sm2.h
index 613fa34022762b082f674dadf0703f3840a348b3..23e38952b2a5e606d101675c9e8d731c54aea7a2 100644
--- a/crypto/include/internal/sm2.h
+++ b/crypto/include/internal/sm2.h
@@ -15,10 +15,6 @@
 
 # ifndef OPENSSL_NO_SM2
 
-#  ifdef __cplusplus
-extern "C" {
-#  endif
-
 #  include <openssl/ec.h>
 
 /* The default user id as specified in GM/T 0009-2012 */
@@ -74,9 +70,5 @@ int sm2_decrypt(const EC_KEY *key,
                 const uint8_t *ciphertext,
                 size_t ciphertext_len, uint8_t *ptext_buf, size_t *ptext_len);
 
-#  ifdef __cplusplus
-}
-#  endif
-
 # endif /* OPENSSL_NO_SM2 */
 #endif
diff --git a/crypto/include/internal/sm2err.h b/crypto/include/internal/sm2err.h
index 9a7e2b62758cddb5e7c5b1d4eda1997fe6c52994..f32d26c04ba77af604b0966eba489932818290e4 100644
--- a/crypto/include/internal/sm2err.h
+++ b/crypto/include/internal/sm2err.h
@@ -15,9 +15,6 @@
 
 # ifndef OPENSSL_NO_SM2
 
-#  ifdef  __cplusplus
-extern "C"
-#  endif
 int ERR_load_SM2_strings(void);
 
 /*
diff --git a/crypto/include/internal/store_int.h b/crypto/include/internal/store_int.h
index 9966aefa679754ae892cfee25104fbd635d698f4..0125aae03efad6af167dc943de7e36b67b5cd422 100644
--- a/crypto/include/internal/store_int.h
+++ b/crypto/include/internal/store_int.h
@@ -14,10 +14,6 @@
 # include <openssl/store.h>
 # include <openssl/ui.h>
 
-# ifdef  __cplusplus
-extern "C" {
-# endif
-
 /*
  * Two functions to read PEM data off an already opened BIO.  To be used
  * instead of OSSLSTORE_open() and OSSLSTORE_close().  Everything is done
@@ -27,7 +23,4 @@ OSSL_STORE_CTX *ossl_store_attach_pem_bio(BIO *bp, const UI_METHOD *ui_method,
                                           void *ui_data);
 int ossl_store_detach_pem_bio(OSSL_STORE_CTX *ctx);
 
-# ifdef  __cplusplus
-}
-# endif
 #endif
diff --git a/crypto/seed/seed_locl.h b/crypto/seed/seed_locl.h
index d4a03fc4aa85f5c23b12f7ce70823bf03de6dd54..97c43ef684c672b914242992700858f5e47bb19f 100644
--- a/crypto/seed/seed_locl.h
+++ b/crypto/seed/seed_locl.h
@@ -45,10 +45,6 @@ typedef unsigned int seed_word;
 # endif
 
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 # define char2word(c, i)  \
         (i) = ((((seed_word)(c)[0]) << 24) | (((seed_word)(c)[1]) << 16) | (((seed_word)(c)[2]) << 8) | ((seed_word)(c)[3]))
 
@@ -113,8 +109,4 @@ extern "C" {
         (X1) ^= (T0);                            \
         (X2) ^= (T1)
 
-#ifdef  __cplusplus
-}
-#endif
-
 #endif                          /* HEADER_SEED_LOCL_H */
diff --git a/crypto/x509v3/v3_admis.h b/crypto/x509v3/v3_admis.h
index 2f1e76d78ef42f568a6d71fb42fd62355dbbc4b1..fa23fc761759f26725ee9c5ec1f5c39600fcc201 100644
--- a/crypto/x509v3/v3_admis.h
+++ b/crypto/x509v3/v3_admis.h
@@ -10,10 +10,6 @@
 #ifndef HEADER_V3_ADMISSION_H
 # define HEADER_V3_ADMISSION_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 struct NamingAuthority_st {
     ASN1_OBJECT* namingAuthorityId;
     ASN1_IA5STRING* namingAuthorityUrl;
@@ -39,7 +35,4 @@ struct AdmissionSyntax_st {
     STACK_OF(ADMISSIONS)* contentsOfAdmissions;
 };
 
-#ifdef  __cplusplus
-}
-#endif
 #endif
diff --git a/e_os.h b/e_os.h
index 5071af6231970aa14df275e778f022857afea12d..5769029b7281cd4b05a015c6ed4ca61e4057b5ea 100644
--- a/e_os.h
+++ b/e_os.h
@@ -22,10 +22,6 @@
  * outside; this file e_os.h is not part of the exported interface.
  */
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 # ifndef DEVRANDOM
 /*
  * set this to a comma-separated list of 'random' device files to try out. By
@@ -325,8 +321,4 @@ struct servent *getservbyname(const char *name, const char *proto);
 # define CRYPTO_memcmp memcmp
 #endif
 
-#ifdef  __cplusplus
-}
-#endif
-
 #endif
diff --git a/include/internal/conf.h b/include/internal/conf.h
index ada3f92b4d86c64e5e5ad933116228998fc8e18e..23a9c3b4744666d81dd104b15b9a0ddd58d832bc 100644
--- a/include/internal/conf.h
+++ b/include/internal/conf.h
@@ -12,11 +12,6 @@
 
 #include <openssl/conf.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-
 struct ossl_init_settings_st {
     char *appname;
 };
@@ -25,8 +20,4 @@ void openssl_config_int(const char *appname);
 void openssl_no_config_int(void);
 void conf_modules_free_int(void);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif
diff --git a/include/internal/constant_time_locl.h b/include/internal/constant_time_locl.h
index d23f515c4ffd2a0051e381da9cbc58de90210efd..82ff74652ecca58f74c11c6754b52a176cf530b7 100644
--- a/include/internal/constant_time_locl.h
+++ b/include/internal/constant_time_locl.h
@@ -14,10 +14,6 @@
 # include <string.h>
 # include <openssl/e_os2.h>              /* For 'ossl_inline' */
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /*-
  * The boolean methods return a bitmask of all ones (0xff...f) for true
  * and 0 for false. This is useful for choosing a value based on the result
@@ -328,8 +324,4 @@ static ossl_inline void constant_time_lookup(void *out,
     }
 }
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif                          /* HEADER_CONSTANT_TIME_LOCL_H */
diff --git a/include/internal/cryptlib.h b/include/internal/cryptlib.h
index 8a96de9847aaac545854d54c63a8606b6928b9b9..2808fe7eea068aeca09b06e5c4eafe1ba7e22a6c 100644
--- a/include/internal/cryptlib.h
+++ b/include/internal/cryptlib.h
@@ -25,10 +25,6 @@
 # include <openssl/err.h>
 # include "internal/nelem.h"
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 #ifdef NDEBUG
 # define ossl_assert(x) ((x) != 0)
 #else
@@ -96,8 +92,4 @@ void *openssl_fopen(const char *filename, const char *mode);
 
 uint32_t OPENSSL_rdtsc(void);
 
-#ifdef  __cplusplus
-}
-#endif
-
 #endif
diff --git a/include/internal/dso.h b/include/internal/dso.h
index 402a76f6dfc50dd558c98241c6440d886580acca..3e67d5053a1510a11cecf053749e5775dbcd69fb 100644
--- a/include/internal/dso.h
+++ b/include/internal/dso.h
@@ -13,10 +13,6 @@
 # include <openssl/crypto.h>
 # include "internal/dsoerr.h"
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /* These values are used as commands to DSO_ctrl() */
 # define DSO_CTRL_GET_FLAGS      1
 # define DSO_CTRL_SET_FLAGS      2
@@ -166,7 +162,4 @@ void *DSO_global_lookup(const char *name);
 
 int ERR_load_DSO_strings(void);
 
-# ifdef  __cplusplus
-}
-# endif
 #endif
diff --git a/include/internal/dsoerr.h b/include/internal/dsoerr.h
index a54a18545e3c75bf5bc16bc144dcbe51a1734eb7..ac6bdcd038b376c1f5553ca2220313bb1c283d08 100644
--- a/include/internal/dsoerr.h
+++ b/include/internal/dsoerr.h
@@ -15,9 +15,6 @@
 
 # ifndef OPENSSL_NO_DSO
 
-#  ifdef  __cplusplus
-extern "C"
-#  endif
 int ERR_load_DSO_strings(void);
 
 /*
diff --git a/include/internal/o_dir.h b/include/internal/o_dir.h
index f18fc6708efe3d30356b88311999805a4b77b41f..f8926877d8387fd90343af9c2924e2d7317b8641 100644
--- a/include/internal/o_dir.h
+++ b/include/internal/o_dir.h
@@ -39,10 +39,6 @@
 #ifndef O_DIR_H
 # define O_DIR_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 typedef struct OPENSSL_dir_context_st OPENSSL_DIR_CTX;
 
 /*
@@ -53,8 +49,4 @@ const char *OPENSSL_DIR_read(OPENSSL_DIR_CTX **ctx, const char *directory);
 /* returns 1 on success, 0 on error */
 int OPENSSL_DIR_end(OPENSSL_DIR_CTX **ctx);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif                          /* LPDIR_H */
diff --git a/ssl/packet_locl.h b/ssl/packet_locl.h
index 8e553e62b5ac29e731cb65da6d4e83c29fb20670..fd32a640112aa39a56946b931967b8010c3ee8a7 100644
--- a/ssl/packet_locl.h
+++ b/ssl/packet_locl.h
@@ -18,10 +18,6 @@
 
 # include "internal/numbers.h"
 
-# ifdef __cplusplus
-extern "C" {
-# endif
-
 typedef struct {
     /* Pointer to where we are currently reading from */
     const unsigned char *curr;
@@ -875,8 +871,4 @@ unsigned char *WPACKET_get_curr(WPACKET *pkt);
 /* Release resources in a WPACKET if a failure has occurred. */
 void WPACKET_cleanup(WPACKET *pkt);
 
-# ifdef __cplusplus
-}
-# endif
-
 #endif                          /* HEADER_PACKET_LOCL_H */